Methods for treating contaminated water

Abstract

To provide a simple and efficient method for treating contaminated water.SOLUTION: A method for treating contaminated water includes: a mixing step of mixing contaminated water containing 1,4-dioxane and an oxidant to form a mixture; and a contacting step of contacting the mixture with one or more selected from the group consisting of concrete, steel slags, and fly ashes, wherein the contaminated water may further contain manganese and chloride ions that inhibit oxidation reaction of 1,4-dioxane.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for treating contaminated water.

Background Art

[0002] In recent years, contamination of groundwater by organic pollutants has become a problem. An example of the organic pollutants is 1,4-dioxane, which is frequently used as an aprotic solvent. 1,4-dioxane is released into the environment not only from waste liquids after being used for solvent purposes, but also from by-products during surfactant synthesis, leaching from waste, domestic wastewater, and the like.

[0003] In general, as a method for purifying contaminated groundwater, groundwater is pumped up and subjected to water treatment such as oxidative decomposition treatment (for example, refer to Patent Documents 1 and 2). As methods for removing 1,4-dioxane, for example, Fenton treatment, alkali catalyst treatment using sodium persulfate, advanced oxidation process using ozone and the like are known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of Invention

Problems to be Solved by the Invention

[0005] Incidentally, the Fenton treatment and the alkali catalyst treatment using sodium persulfate are methods that are performed almost in a batch mode, and the treatment is difficult to control, so that efficient continuous treatment could not be performed. In addition, the advanced oxidation process using ozone requires preparation of equipment for producing ozone, which causes problems of complicated equipment and high cost.

[0006] The present invention aims to provide a method for treating contaminated water that can treat contaminated water simply and efficiently. [Means for solving the problem]

[0007] The inventors investigated a method of bringing concrete and contaminated water into contact in order to treat contaminated water in a continuous process. This is because water that passes through the voids (hereinafter sometimes referred to as voids) of concrete becomes alkaline, and the permeability coefficient of the material can be easily adjusted compared to other materials.

[0008] More specifically, because concrete contains alkalis such as calcium hydroxide, bringing water contaminated with 1,4-dioxane into contact with the concrete makes it alkaline, which facilitates treatment with oxidizing agents such as persulfates.

[0009] Furthermore, concrete members, or layers constructed by accumulating concrete, allow for adjustment of the permeability coefficient of the entire layer or member by adjusting the void ratio (also called interstitial void ratio). Therefore, conditions can be established to ensure sufficient treatment time for contaminated water to continuously treat 1,4-dioxane.

[0010] As a result of further investigation by the present inventors, it was found that by bringing contaminated water and an oxidizing agent into contact with concrete, the 1,4-dioxane contained in the contaminated water is decomposed, and as a result, the contaminated water can be treated efficiently.

[0011] Specifically, one embodiment of the present invention is a method for treating contaminated water, comprising a mixing step of mixing contaminated water containing 1,4-dioxane with an oxidizing agent to form a mixture, and a contact step of bringing the mixture into contact with concrete.

[0012] Furthermore, the inventors investigated a method of contacting contaminated water with steel slag and / or fly ash, which are commonly used as admixtures in concrete. As a result, they found that by contacting a mixture of contaminated water and an oxidizing agent with steel slag and / or fly ash, the decomposition of 1,4-dioxane contained in the contaminated water can be efficiently achieved.

[0013] Specifically, another embodiment of the present invention is a method for treating contaminated water, comprising a mixing step of mixing contaminated water containing 1,4-dioxane with an oxidizing agent to form a mixture, and a contact step of bringing the mixture into contact with steel slag and fly ash. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a method for treating contaminated water that can treat contaminated water simply and efficiently. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a schematic diagram of an example embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram of an example of another embodiment of the present invention. [Figure 3] Figure 3 is a line graph showing the 1,4-dioxane concentration of the mixture before and after passing through a porous concrete column. [Figure 4] Figure 4 is a line graph showing the pH of the mixture before and after passing through a porous concrete column. [Figure 5] Figure 5 is a line graph showing the 1,4-dioxane concentration of the mixture before and after passing through the concrete rubble column. [Figure 6] Figure 6 is a line graph showing the pH of the mixture before and after passing through the concrete rubble column. [Figure 7] Figure 7 is a line graph showing the 1,4-dioxane concentration of the mixture (containing oxidation reaction inhibitors) before and after passing through the concrete rubble column. [Figure 8]Figure 8 is a line graph showing the manganese concentration of the mixture (containing an oxidation reaction inhibitory substance) before and after passing through the concrete waste column. [Figure 9] Figure 9 is a line graph showing the 1,4-dioxane concentration of the mixture before and after passing through the steelmaking slag column. [Figure 10] Figure 10 is a line graph showing the pH of the mixture before and after passing through the steelmaking slag column. [Figure 11] Figure 11 is a line graph showing the 1,4-dioxane concentration of the mixture before and after passing through the fly ash column. [Figure 12] Figure 12 is a line graph showing the pH of the mixture before and after passing through the fly ash column. [Mode for Carrying Out the Invention]

[0016] (Method for treating contaminated water) The method for treating contaminated water of the present invention includes a mixing step and a contacting step, and further includes other steps as necessary.

[0017] <Mixing Step> The mixing step is a step of mixing contaminated water containing 1,4-dioxane (hereinafter, may be abbreviated as "contaminated water") with an oxidizing agent. The mixing step may be performed before the contacting step described later, or may be performed such that the contaminated water and the oxidizing agent are mixed during the contacting step. Note that in the mixing step, a compound other than the oxidizing agent such as a surfactant may be mixed as long as the effects of the present invention are not impaired.

[0018] The method for mixing the contaminated water and the oxidizing agent is not particularly limited and can be appropriately selected according to the purpose. For example, a method can be used in which contaminated water containing 1,4-dioxane is caused to flow through a line, and the oxidizing agent is injected directly into this line.

[0019] Alternatively, it is also possible to use a method of combining a tank containing contaminated water containing 1,4-dioxane, a tank containing a solution containing an oxidizing agent, and a three-way cock (details will be described later).

[0020] <<Contaminated water>> The contaminated water to be treated in this embodiment contains 1,4-dioxane, and also contains manganese and chloride ions.

[0021] When contaminated water containing 1,4-dioxane is treated with oxidation, the presence of manganese and chloride ions acts as an inhibitor of oxidation (see, for example, "Inhibitory Factors in Groundwater in the Decomposition of 1,4-Dioxane by Persulfuric Acid and Their Reduction," Yuki Mizushima, Wataru Haruyama, Hiroki Ogata, Kenji Nishida, and Hiroshi Nakazawa (Proceedings of the 23rd Research Meeting on Groundwater and Soil Contamination and its Prevention Measures (2017), pp. 272-273)). However, with the wastewater treatment method of the present invention, the oxidation reaction of 1,4-dioxane can proceed even in the presence of manganese and chloride ions.

[0022] There are no particular restrictions on the content of 1,4-dioxane, manganese, and chloride ions, and they can be appropriately selected depending on the purpose.

[0023] <<Oxidizing agent>> The oxidizing agent is used to oxidize 1,4-dioxane. Examples of oxidizing agents include peroxodisulfates such as sodium persulfate (SPS), potassium persulfate, and ammonium persulfate, as well as potassium peroxomonosulfate (trade name: Oxon®) and sodium percarbonate. These may be used individually or in combination of two or more. Among these, sodium persulfate is preferred. The oxidizing agent may be in solid or liquid form, or it may be mixed with a suitable solvent to form a liquid. Persulfates may be synthesized as appropriate or commercially available. Examples of commercially available persulfates include sodium persulfate (manufactured by Mitsubishi Gas Chemical Company, Inc.).

[0024] [Mixing ratio (concentration of oxidizing agent in contaminated water)] The concentration of the oxidizing agent in the contaminated water is preferably 0.05% to 3%, and more preferably 0.2% to 2%. As an example of a method for adjusting the concentration of an oxidizing agent in contaminated water, the following method uses sodium persulfate. A 30% sodium persulfate solution is added to 1 m³ of contaminated water. 3 By injecting 17 liters per unit area, the concentration of sodium persulfate in the contaminated water can be reduced to 0.5%.

[0025] <<Alkaline Materials>> In the mixing process, an alkaline material may be added in addition to the contaminated water and oxidizing agent. The alkaline material is not particularly limited as long as it is expected to promote the oxidation reaction by the oxidizing agent, and examples include calcium carbonate, magnesium oxide, magnesium carbonate, calcium oxide, calcium hydroxide, magnesium, magnesium hydroxide, incinerated ash such as coal ash, solidified papermaking sludge, solidified alumina silica such as geopolymer, solidified water glass (sodium silicate), seashells and crushed seashells, perlite, granular glass, crushed glass, foamed glass, and granular solidified alkaline soil. Alkaline materials may be added to a mixture of contaminated water and an oxidizing agent, or they may be mixed with concrete, steel slag, or fly ash.

[0026] <Contact process> The contact process involves bringing the aforementioned mixture into contact with concrete, steel slag, or fly ash. Contact as used herein includes contact between a portion of the concrete, steel slag, or fly ash and a portion of the mixture, and the passage of the mixture through the voids in the concrete, steel slag, or fly ash.

[0027] There are no particular limitations on the means of bringing the mixture into contact with concrete, steel slag, or fly ash, and can be appropriately selected depending on the purpose. For example, one method is to spread concrete, steel slag, or fly ash inside a water tank and pour the mixture from the bottom of the tank.

[0028] Furthermore, there are no particular limitations on other means of bringing the mixture into contact with concretes, steel slag, and / or fly ash, and these can be appropriately selected depending on the purpose. For example, one method is to fill the inside of a column with at least one selected from the group consisting of concretes, steel slag, and fly ash, and then inject the mixture into the column.

[0029] <<Concrete products>> In this specification, "concrete" is a broad concept encompassing materials that use cement as a binder, and specific examples include ordinary concrete and porous concrete, as well as mortar and cement alone.

[0030] Here, porous concrete generally refers to concrete that does not use fine aggregate, or has a lower amount of fine aggregate than ordinary concrete. Because porous concrete is a porous concrete with more voids than ordinary concrete, it is easy to bring into contact with mixtures. There are no limitations on the pore size of porous concrete in this invention, and it can be appropriately selected to meet the necessary design conditions.

[0031] Regarding the number, shape, and size of concrete materials to be in contact with the mixture, it is possible to use not only a single component but also a collection of multiple concrete blocks (hereinafter referred to as "concrete blocks"). A combination of multiple types or sizes of concrete blocks may be used. Therefore, it is also possible to use a porous concrete component in combination with multiple small-diameter concrete blocks.

[0032] Multiple concrete blocks can also be laid in layers, as shown in layer 3 of Figure 1 (details will be described later). In this case, by adjusting the gaps between the concrete blocks, it is possible to construct the layer so that the permeability coefficient of the entire layer is the value set in the design. The permeability coefficient is set to an appropriate value depending on the conditions, but 1 × 10 -3 It is preferable to set the rate to cm / sec or higher.

[0033] Concrete rubble can be used as concrete blocks. Concrete rubble is waste from concrete, mortar, or cement, and is generated, for example, from demolition work or from crushed by-products such as residues generated during the manufacture of concrete or mortar. Concrete rubble may include fragments with a maximum long side (maximum particle size) of 500 mm or less.

[0034] There is no particular lower limit to the maximum particle size of concrete blocks, and it can be appropriately selected depending on the purpose, but 1 mm or larger is preferable. Furthermore, when using concrete lumps with a maximum particle size of 1 mm or less, a method may be used in which the lumps are packed into bags such as sandbags, and the mixture that passes through the bag comes into contact with the concrete lumps inside the bag.

[0035] <<Steel Slag>> In this specification, "steel slag" may refer to either blast furnace slag or steelmaking slag. Blast furnace slag includes blast furnace slowly cooled slag obtained by slowly cooling molten slag discharged from a blast furnace, and granulated slag obtained by rapid cooling. Steelmaking slag includes converter slag produced in a converter when oxygen is blown onto pig iron for oxidation refining, and electric furnace slag produced in an electric furnace when iron scrap is refined. Converter slag includes decarburized slag, dephosphorized slag, demanganese slag, etc., obtained through the impurity separation process. Electric furnace slag includes oxidized slag produced by oxidation refining and reduced slag produced by reduction refining. Although converter steelmaking slag is discharged in large quantities, approximately 10 million tons per year, the reuse rate of converter steelmaking slag is low compared to blast furnace slag, which is increasingly reused as road infrastructure material.

[0036] Steel slag contains silicon dioxide, calcium oxide, magnesium oxide, and aluminum oxide, among other things. While there are no particular limitations on the type of steel slag used, it is preferable to use steelmaking slag from the standpoint of resource recycling.

[0037] The shape and size of the steel slag are not particularly limited, but from the viewpoint of adjusting the flow rate of the mixture passing through, the average particle diameter of the steel slag is preferably 1 to 80 mm, and more preferably 2 to 40 mm. The average particle diameter of the steel slag can be measured using a vibrating sieving device.

[0038] <<Fly ash>> In this specification, "fly ash" refers to the ash produced when coal is burned. Fly ash is not particularly limited, but examples include ash produced when pulverized coal is burned in the boilers of a coal-fired power plant, and which is then collected by an electrostatic precipitator.

[0039] Fly ash contains pozzolanes, which are composed of silicon dioxide (SiO2), aluminum oxide (Al2O3), etc. Fly ash is classified into four types, types I to IV, according to JIS A 6201:2015 "Fly ash for concrete," based on differences in fineness and loss on ignition, and any of these types may be used.

[0040] <Other processes> Other steps are not particularly limited as long as they do not impair the effects of the present invention, and can be appropriately selected depending on the purpose.

[0041] (Specific examples of methods for treating contaminated water) Here, a specific example of the contaminated water treatment method of the present invention will be explained with reference to the drawings. Figure 1 is a schematic diagram of an example of an apparatus used in the contaminated water treatment method of the present invention. In the example in Figure 1, the contaminated water is assumed to flow from left to right.

[0042] First, contaminated water containing 1,4-dioxane is passed through line 1 using a water-passing means such as a pump. Next, an oxidizing agent is added through line 2, which is connected to line 1, using an adding means such as a pump. The contaminated water flowing through line 1 and the oxidizing agent are mixed, forming a mixture of contaminated water and oxidizing agent.

[0043] As the flow of contaminated water continues, the formed mixture permeates through layer 3, which is laid or filled with concrete, steel slag, or fly ash. As the mixture passes through layer 3 and comes into contact with the concrete, steel slag, or fly ash, 1,4-dioxane is oxidized by the oxidizing agent. The concrete, steel slag, or fly ash accelerates the oxidation reaction of 1,4-dioxane.

[0044] Furthermore, concrete, steel slag, or fly ash trap manganese, which inhibits the oxidation reaction of 1,4-dioxane. Therefore, even if the contaminated water contains manganese and chloride ions, the oxidation reaction of 1,4-dioxane will not be inhibited.

[0045] The fluid that has passed through layer 3 reaches line 4 at the top of the layer. The fluid is stored in a water storage means, such as a tank (not shown), via line 4. The fluid that has passed through layer 3 includes, for example, water from which 1,4-dioxane has been decomposed, and oxidizing agent that was not used in the oxidation reaction.

[0046] Figure 2 is a schematic diagram of an example of another apparatus used in the treatment of contaminated water contaminated with 1,4-dioxane.

[0047] The apparatus in Figure 2 includes two tanks 11 and 12, two pumps 21 and 22, three three-way cocks 31, 32 and 33, and two columns 100 and 200. Tank 11 and pump 21, and tank 12 and pump 22 are connected via lines. Pump 21 and three-way cock 31, and pump 22 and three-way cock 31 are connected via lines 13 and 23, respectively. Furthermore, three-way cock 31, column 100, three-way cock 32, column 200, and three-way cock 33 are connected in series via lines in this order.

[0048] Tanks 11 and 12 can store contaminated water containing 1,4-dioxane or solutions containing an oxidizing agent. The tanks used are not particularly limited and include, for example, plastic containers, plastic buckets with lids, oil cans, 18-liter cans, stainless steel tanks, etc.

[0049] Pumps 21 and 22 have the function of passing contaminated water containing 1,4-dioxane or a solution containing an oxidizing agent, stored in tanks 11 and 12, through lines 13 and 23 at a predetermined flow rate. The pumps used are not particularly limited and include, for example, gear pumps, syringe pumps, magnetic pumps, plunger pumps, screw pumps, diaphragm pumps, piston pumps, rotary pumps, tube pumps, suction pumps, pressure pumps, plunger pumps, etc.

[0050] The three-way stopcock 31 has the function of mixing the contaminated water containing 1,4-dioxane and the solution containing the oxidizing agent flowing through lines 13 and 23 to form a mixture. The three-way stopcocks 31, 32, and 33 can all be used to sample the mixture. The method of mixing the contaminated water containing 1,4-dioxane and the solution containing the oxidizing agent is not particularly limited, and in addition to the three-way stopcock, a T-tube, a Y-tube, etc. may be used.

[0051] Column 100 has a contact layer 110 filled with concrete, steel slag, or fly ash. The inlet and outlet of column 100 can be sealed with stoppers 101a and 101b. The stoppers are not particularly limited, and for example, rubber stoppers can be used. Retaining members 102a and 102b may also be provided at the inlet and outlet of column 100. The retaining members are not particularly limited, and for example, wire mesh, strainers, perforated plates, glass beads, etc. can be used individually or in appropriate combinations. Figure 2 shows an example where two columns 100 and 200 are connected in series. Alternatively, three or more columns having a contact layer filled with concrete, steel slag, or fly ash may be connected in series, or two or more columns may be connected in parallel. When multiple columns are connected, it becomes easier to sample the solution in each line by installing three-way stopcocks (e.g., three-way stopcocks 32, 33, etc.) between each column.

[0052] Next, we will explain an example of how to use the device shown in Figure 2. First, contaminated water containing 1,4-dioxane is stored in tank 11 and then pumped 12 to flow it through line 13. Additionally, a solution containing an oxidizing agent is stored in tank 21 and pumped 22 to flow it through line 23. The contaminated water containing 1,4-dioxane flowing through line 13 and the solution containing the oxidizing agent flowing through line 23 are mixed via a three-way stopcock 31, forming a mixture of contaminated water and the oxidizing agent.

[0053] The mixture of contaminated water and oxidizer passes through the contact layer in column 100. While the mixture passes through the contact layer 110, it can be brought into contact with concrete, steel slag, or fly ash. When the mixture of contaminated water and oxidizing agent passes through the contact layer 110 and comes into contact with concrete, steel slag, or fly ash, the oxidation reaction of 1,4-dioxane is promoted, and the 1,4-dioxane contained in the contaminated water can be efficiently decomposed. [Examples]

[0054] The following describes examples of the disclosed technology, but the disclosed technology is not limited to these examples.

[0055] (Example 1) 1,4-dioxane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in deionized water to prepare 1,4-dioxane aqueous solution (concentration: 1 mg / L) with a 1,4-dioxane concentration of 1 mg / L. Next, manganese sulfate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in 1,4-dioxane water to achieve a manganese concentration of 50 mg / L, and sodium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved to achieve a chloride ion concentration of 1,300 mg / L, creating simulated contaminated water. A manganese ion concentration of 50 mg / L corresponds to a manganese sulfate concentration of 137 mg / L, and a chloride ion concentration of 1,300 mg / L corresponds to a sodium chloride concentration of 2,140 mg / L.

[0056] Porous concrete (permeable colored gravel concrete that hardens, manufactured by Terada Co., Ltd., gravel particle size: 2-5 mm) was filled into an acrylic pipe with an inner diameter of 10 cm and a length of 30 cm to a thickness of 20 cm. Rubber stoppers were installed at the top and bottom of the acrylic pipe. Simulated contaminated water was passed through this acrylic pipe at a rate of 3.3 mL / min, and SPS water (3% concentration) as an oxidizing agent was passed through at a rate of 0.7 mL / min. The simulated contaminated water and the oxidizing agent were mixed and brought into contact with porous concrete.

[0057] Water samples were taken at the column outlet when 100 L of water was passed through. The 1,4-dioxane concentration was measured using a gas chromatograph-mass spectrometer (GCMS-QP® 2010 Ultra, manufactured by Shimadzu Corporation), the pH was measured using a glass electrode hydrogen ion concentration meter (MM43X, manufactured by Toa DKK Corporation), and the manganese concentration was measured using a polarized Zeeman atomic absorption spectrophotometer (ZA3300, manufactured by Hitachi High-Tech Science Corporation). The measurement results are shown in Table 1.

[0058] [Table 1]

[0059] As is clear from the results in Table 1, the 1,4-dioxane concentration after the contact process was well below the environmental standard value (0.05 mg / L). Furthermore, the manganese concentration after the contact process was significantly reduced. Therefore, the results in Table 1 show that the wastewater treatment method of the present invention is highly effective in treating 1,4-dioxane. In addition to this effect, it was revealed that even in the presence of manganese and chloride ions, which are inhibitors of the oxidation reaction of 1,4-dioxane, manganese can be removed and the oxidation reaction of 1,4-dioxane can proceed.

[0060] (Example 2: Porous concrete) The changes in 1,4-dioxane concentration and pH were measured when a mixture formed by mixing contaminated water contaminated with 1,4-dioxane with a solution containing SPS was passed through a column packed with porous concrete (hereinafter also referred to as the "porous concrete column"). The 1,4-dioxane concentration and pH were measured in the same manner as in Example 1. The method used to mix contaminated water and SPS and pass the mixture through the porous concrete column was the one shown in Figure 2. The following provides a more detailed explanation of the preparation of the porous concrete column, the preparation of various solutions, and the water flow process.

[0061] <Fabrication of porous concrete columns> A plastic column (made of acrylic pipe) with an inner diameter of 10 cm and a height of 30 cm was used. The inlet end of the column (solution inlet and outlet) was sealed with a rubber stopper. With the inlet of the column facing downwards, a wire mesh (stainless steel, 40 mesh, wire diameter 0.18 mm) was placed on top of the rubber stopper, a layer of glass beads (average diameter 5 mm, manufactured by Toshin Riko Co., Ltd.) was placed on top of the wire mesh, and a perforated plate (made of polyvinyl chloride) was laid on top of the glass beads. Porous concrete was filled on top of the perforated plate to a height of 20 cm to form a porous concrete layer. Furthermore, the top of the porous concrete layer was covered with wire mesh, a layer of glass beads was placed on top of the wire mesh, and finally the outlet end was sealed with a rubber stopper. The porous concrete was prepared by adding cement milk (60 g cement, 25 mL tap water) of blast furnace cement type B to 500 g of river gravel (particle size 5-30 mm) (moisture content 2.9%) and mixing. The weight of the porous concrete used for filling was approximately 2500g per column. Five columns having the porous concrete layer described above (hereinafter also referred to as "porous concrete columns") were prepared and connected in series via a line. A three-way stopcock was installed before the first column and between each column to allow sampling of the mixture flowing through each line.

[0062] <Preparation of various solutions> 1,4-dioxane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in tap water to prepare 1,4-dioxane water with a concentration of 0.5 mg / L, and this was placed in a plastic container. Next, SPS (manufactured by Fujifilm Wako Pure Chemical Industries) was dissolved in tap water to prepare 6 (w / w)% SPS water, which was then placed in a separate plastic container.

[0063] <Water flow> 1,4-dioxane water from a poly tank was supplied to the line at a flow rate of 1.4 mL / min using a tube pump (manufactured by Tokyo Rikakikai), and SPS water from another poly tank was supplied to the line at a flow rate of 0.7 mL / min using the same tube pump. These were mixed using a three-way stopcock and then passed through a porous concrete column. Sampling was performed using three-way stopcocks placed before the first column and between each column.

[0064] <Experimental Results> The results of measuring the 1,4-dioxane concentration and pH of the mixture sampled from each three-way stopcock are shown in Figures 3 and 4, respectively. The 1,4-dioxane concentration of the mixture before passing it through the column remained at approximately 0.37–0.45 mg / L (see "Aqueous Solution" in Figure 3). As the mixture passed through each column, the 1,4-dioxane concentration gradually decreased, and after passing through the fifth column, the 1,4-dioxane concentration in the mixture was below the groundwater environmental standard value of 0.05 mg / L (see Figure 3). Furthermore, the pH of the mixture gradually shifted towards the alkaline side as it passed through each column (see Figure 4). This is presumed to be due to the presence of alkalis, including calcium hydroxide, in the porous concrete.

[0065] (Example 3: Concrete rubble) The changes in 1,4-dioxane concentration and pH were measured when a mixture formed by mixing contaminated water contaminated with 1,4-dioxane with a solution containing SPS was passed through a concrete rubble column. The 1,4-dioxane concentration and pH were measured in the same manner as in Example 1. The method used to mix contaminated water and SPS and pass the mixture through the concrete rubble column was the one shown in Figure 2. The following provides a more detailed explanation of the preparation of the concrete rubble column, the preparation of various solutions, and the water flow process.

[0066] <Preparation of concrete rubble columns> For the concrete rubble, we used RC-40 recycled concrete crushed stone, which was sieved through a 40mm mesh sieve. The material that passed through this sieve was then sieved again through a 9.5mm mesh sieve, and the remaining material was used. The concrete glass column was prepared in the same manner as the porous concrete column in Example 2. Five concrete rubble columns were prepared and connected in series. Three-way stopcocks were installed before the first column and between each column to allow sampling of the mixture flowing through each line.

[0067] <Preparation of various solutions> 1,4-dioxane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in deionized water to prepare 1,4-dioxane water with a concentration of 1.5 mg / L, and this was placed in a plastic container. Next, SPS (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in tap water to prepare 6 (w / w) SPS water, which was then placed in a separate plastic container.

[0068] <Water flow> 1,4-dioxane water from a poly tank was supplied to the line at a flow rate of 1.4 mL / min using a tube pump, and SPS water from another poly tank was supplied to the line at a flow rate of 0.7 mL / min using a tube pump. These were mixed using a three-way stopcock and then passed through the concrete rubble column. Sampling was performed using three-way stopcocks placed before the first column and between each column.

[0069] <Experimental Results> The results of measuring the 1,4-dioxane concentration and pH of the mixture sampled from each three-way stopcock are shown in Figures 5 and 6, respectively. The 1,4-dioxane concentration of the mixture before passing it through the column remained at approximately 1.0 mg / L due to dilution with SPS water (see "Water for Passing Through" in Figure 5). As the mixture passed through each column, the 1,4-dioxane concentration in the mixture gradually decreased. After passing through the fifth column, the 1,4-dioxane concentration in the mixture was 0.02-0.03 mg / L, which was below the groundwater environmental standard value of 0.05 mg / L (see Figure 5). Furthermore, the pH of the mixture gradually shifted towards the alkaline side as it passed through each column (see Figure 6). This is presumed to be due to the presence of alkalis, including calcium hydroxide, in the concrete rubble.

[0070] (Example 4: Concrete rubble (contaminated water contains an oxidation reaction inhibitor)) A mixture was formed by mixing contaminated water contaminated with 1,4-dioxane with a solution containing SPS. Manganese and chloride ions, which inhibit oxidation reactions, were then added to the mixture, and the changes in the concentration of 1,4-dioxane and manganese were measured when this mixture was passed through a concrete rubble column. The concentrations of 1,4-dioxane and manganese were measured in the same manner as in Example 1. The method used to mix contaminated water containing manganese and chloride ions (hereinafter also referred to as "simulated contaminated water 2") with SPS and pass the mixture through the concrete rubble column was the method shown in Figure 2. The following describes in more detail the preparation of the concrete rubble column, the preparation of various solutions, and the passage of water through the column.

[0071] <Preparation of concrete rubble columns> A concrete rubble column was prepared using the same method as in Example 3. Five concrete rubble columns were prepared and connected in series. Three-way stopcocks were installed before the first column and between each column to allow sampling of the mixture flowing through each line.

[0072] <Preparation of various solutions> 1,4-dioxane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in deionized water to prepare 1,4-dioxane water with a concentration of 1.0 mg / L. Next, manganese sulfate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in the above 1,4-dioxane water to achieve a manganese concentration of 50 mg / L (137 mg / L as manganese sulfate), and sodium chloride was dissolved to achieve a chloride ion concentration of 1300 mg / L (2140 mg / L as sodium chloride). This was designated as simulated contaminated water 2. Simulated contaminated water 2 was placed in a plastic container. Separately, SPS (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in tap water to prepare 6 (w / w) SPS water, which was then placed in a separate plastic container.

[0073] <Water flow> Simulated contaminated water 2 in a poly tank was supplied to the line at a flow rate of 1.4 mL / min using a tube pump, and SPS water from another poly tank was supplied to the line at a flow rate of 0.7 mL / min using a tube pump. These were mixed using a three-way stopcock and then passed through the concrete rubble column. Sampling was performed using three-way stopcocks placed before the first column and between each column.

[0074] <Experimental Results> The results of measuring the 1,4-dioxane and manganese concentrations of the mixture sampled from each three-way stopcock are shown in Figures 7 and 8, respectively. The 1,4-dioxane concentration of the mixture before passing through the column fluctuated between approximately 0.4 and 0.7 mg / L due to variations in the supply flow rate of the SPS water (see "Water Flow Solution" in Figure 7). As the mixture passed through each column, the 1,4-dioxane concentration in the mixture gradually decreased, and after passing through the fifth column, the 1,4-dioxane concentration in the mixture was 0.05 mg / L or less, which was below the groundwater environmental standard value of 0.05 mg / L (see Figure 7). Furthermore, the manganese concentration of the mixture before passing through the column was approximately 47 mg / L. In contrast, the manganese concentration of the mixture after passing through the first column was reduced to less than 1 / 10, and the manganese concentration of the mixture after passing through the second column was reduced to 1 mg / L, indicating a significant decrease in manganese concentration (see Figure 8).

[0075] (Example 5: Steelmaking slag column) The changes in 1,4-dioxane concentration and pH were measured when a mixture formed by mixing contaminated water contaminated with 1,4-dioxane with a solution containing SPS was passed through a steelmaking slag column. The 1,4-dioxane concentration and pH were measured in the same manner as in Example 1. The method used to mix contaminated water and SPS and pass the mixture through the steelmaking slag column was the method shown in Figure 2. The preparation of the steelmaking slag column, the preparation of various solutions, and the flow of water will be described in more detail below.

[0076] <Preparation of steelmaking slag columns> Derinsing slag (particle size 10-40 mm) was used as the steelmaking slag. A steelmaking slag column was prepared in the same manner as in Example 2. Two steelmaking slag columns were prepared and connected in series. Three-way stopcocks were installed before the first column and between each column to allow sampling of the mixture flowing through each line.

[0077] <Preparation of various solutions> 1,4-dioxane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in deionized water to prepare 1,4-dioxane water with a concentration of 1.0 mg / L, and this was placed in a plastic container. Next, SPS (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in tap water to prepare 3 (w / w)% SPS water, which was then placed in a separate plastic container.

[0078] <Water flow> 1,4-dioxane water from a poly tank was supplied to the line at a flow rate of 1.4 mL / min using a tube pump, and SPS water from another poly tank was supplied to the line at a flow rate of 0.7 mL / min using a tube pump. These were mixed using a three-way stopcock and passed through the steelmaking slag column. Sampling was performed using three-way stopcocks placed before the first column and between each column.

[0079] <Experimental Results> The results of measuring the 1,4-dioxane concentration and pH of the mixture sampled from each three-way stopcock are shown in Figures 9 and 10, respectively. The 1,4-dioxane concentration of the mixture before passing through the column remained around 0.6-0.7 mg / L due to dilution with SPS water (see "Condensed Water" in Figure 9). As the mixture passed through each column, the 1,4-dioxane concentration in the mixture gradually decreased. After passing through the second column, the 1,4-dioxane concentration in the mixture was 0.02-0.03 mg / L, which was below the groundwater environmental standard value of 0.05 mg / L (see Figure 9). Furthermore, the pH of the mixture shifted towards the acidic side as it passed through each column. This is presumed to be because the iron in the steelmaking slag reacted, accelerating the oxidation reaction, and sulfuric acid was produced after the oxidation reaction of SPS, causing the pH to shift towards the acidic side (see Figure 10).

[0080] (Example 6: Fly ash column) The changes in 1,4-dioxane concentration and pH were measured when a mixture formed by mixing contaminated water contaminated with 1,4-dioxane with a solution containing SPS was passed through a fly ash column. The 1,4-dioxane concentration and pH were measured in the same manner as in Example 1. The method used to mix contaminated water and SPS and pass the mixture through the fly ash column was the one shown in Figure 2. The preparation of the fly ash column, the preparation of various solutions, and the flow of the water will be explained in more detail below.

[0081] <Preparation of a fly ash column> As fly ash, 500g of river gravel (particle size 5-30mm) (moisture content 2.9%) was mixed with fly ash milk (60g of fly ash type II (manufactured by J-Power Generation Service Co., Ltd.) and 25mL of tap water). Fly ash columns were prepared in the same manner as in Example 2. Approximately 2600g of fly ash was packed into each column. Two fly ash columns were prepared and connected in series. A three-way stopcock was installed before the first column and between each column to allow sampling of the mixture flowing through each line.

[0082] <Preparation of various solutions> 1,4-dioxane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in deionized water to prepare 1,4-dioxane water with a concentration of 0.75 mg / L, and this was placed in a plastic container. Next, SPS (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in tap water to prepare 6 (w / w) SPS water, which was then placed in a separate plastic container.

[0083] <Water flow> 1,4-dioxane water from a poly tank was supplied to the line at a flow rate of 1.4 mL / min using a tube pump, and SPS water from another poly tank was supplied to the line at a flow rate of 0.7 mL / min using a tube pump. These were mixed using a three-way stopcock and passed through the fly ash column. Sampling was performed using three-way stopcocks placed before the first column and between each column.

[0084] <Experimental Results> The results of measuring the 1,4-dioxane concentration and pH of the mixture sampled from each three-way stopcock are shown in Figures 11 and 12, respectively. The 1,4-dioxane concentration of the mixture before passing it through the column remained at approximately 0.6 mg / L due to dilution with SPS water (see "Water for Passing Through" in Figure 11). After passing through the first column, the 1,4-dioxane concentration in the mixture showed some variation, but remained below the groundwater environmental standard of 0.05 mg / L (see Figure 11). Furthermore, the pH of the mixture that passed through columns 1 to 4 showed an acidic value. This is presumed to be due to the high concentration of SPS and the sulfuric acid produced after the oxidation reaction of SPS (see Figure 12).

[0085] From the above, Figures 3, 5, 7, 9, and 11 show that by passing a mixture of contaminated water and SPS through a column packed with porous concrete, concrete rubble, steelmaking slag, or fly ash, the oxidation reaction by SPS can be promoted, and the 1,4-dioxane concentration can be reduced to the groundwater environmental standard value of 0.05 mg / L or less. [Explanation of Symbols]

[0086] 11, 21 tanks 12, 22 pumps Lines 13 and 23 31, 32, 33 Three-way cooktop 100, 200 columns 101a, 101b stopper 102a, 102b Retaining members 110 Contact layer

Claims

1. A mixing step of mixing contaminated water containing 1,4-dioxane with an oxidizing agent to form a mixture, A method for treating contaminated water, comprising a contact step of bringing the mixture into contact with one or more selected from the group consisting of concretes and fly ash, A method for treating contaminated water, wherein the oxidizing agent is at least one of sodium persulfate (SPS), potassium persulfate, peroxodisulfate containing ammonium persulfate, potassium peroxomonosulfate, and sodium percarbonate.

2. The method for treating contaminated water according to claim 1, wherein the contaminated water further contains manganese and chloride ions.

3. The method for treating contaminated water according to claim 1 or 2, wherein the concrete is porous concrete.

4. The method for treating contaminated water according to claim 1 or 2, wherein the concrete materials are concrete rubble.

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